1. Field of the Invention
The invention relates to a vacuum cleaning tool for a vacuum cleaning device comprising a housing in which a brush chamber and a turbine chamber are provided. A working roller, in particular, a brush roller, is arranged in the brush chamber transversely to the working direction of the suction cleaning tool. The working roller penetrates with a peripheral portion a suction slot provided in the bottom of the brush chamber. An air turbine is arranged in the turbine chamber for driving in rotation the working roller. A vacuum airflow of the vacuum cleaning tool enters the brush chamber via the suction slot, flows into the turbine chamber via an intake window provided in a partition between the brush chamber and the turbine chamber, and exits from the turbine chamber through an outlet window of a vacuum connector. Between neighboring vanes of an annular vane arrangement of the air turbine free flow paths to a vane-free center of the air turbine are formed; the vacuum airflow passes through the vane-free center of the air turbine along its path from the intake window to the outlet window of the vacuum connector.
2. Description of the Related Art
Such a vacuum cleaning tool is known from U.S. Pat. No. 5,249,333. It is comprised substantially of a housing with a brush chamber and a turbine chamber. In the brush chamber a brush roller is arranged transversely to the working direction of the vacuum cleaning tool. Its bristles project through the suction slot in the bottom of the brush chamber in order to mechanically act onto the floor surface to be cleaned. The air turbine arranged in the turbine chamber drives by means of a belt drive the brush roller in rotation, wherein the vacuum airflow flowing through the vacuum cleaning tool drives the air turbine.
In order to achieve a higher power output, the air turbine is configured as a direct flow turbine in which between neighboring vanes of an annular vane arrangement free flow paths are formed which allow the vacuum airflow to enter the vane-free center of the air turbine. On its path from the intake window into the turbine chamber and to the outlet window at the vacuum connector the vacuum airflow flows thus twice through the annular vane arrangement so that a high power output can be achieved. As a result of this special flow arrangement of the air turbine, high rotational speeds up to 30,000 rpm are achieved which, however, results in an undesirable noise level increase.
It is an object of the present invention to further develop a vacuum cleaning tool of the aforementioned kind such that for a high power output of the air turbine a lowering of the noise level can be achieved.
In accordance with the present invention, this is achieved in that the intake cross-section of the turbine chamber measured at the partition in a direction transverse to the flow direction is greater than the outlet cross-section of the turbine chamber measured in the same direction at its end facing the outlet window and in that the cross-section of the turbine chamber decreases toward the outlet cross-section such that the turbine chamber tapers in the direction toward the outlet cross-section.
A high power output of the air turbine is achieved in that the turbine chamber is configured, while preventing dead space, such that its walls are positioned with minimal spacing relative to the air turbine. For this purpose, the intake cross-section of the turbine chamber at the level of the partition is configured to be larger than the outlet cross-section of the turbine chamber measured in the same direction and same position at the end facing the outlet window. In this connection, the intermediate cross-sections measured between the intake cross-section and the outlet cross-section in the direction toward the outlet cross-section become smaller so that the turbine chamber tapers in the direction toward the outlet cross-section. This achieves, on the one hand, a combination of the partial flows of the working airflow and of fault flows forming in the turbine chamber, wherein a directed guiding to the outlet window is realized. Accordingly, the airflow is made more uniform; the guiding of the vacuum airflow out of the turbine chamber is assisted in a beneficial way so that the vacuum airflow entering the turbine chamber enters substantially disruption-free the vane-free center of the air turbine.
The configuration of the turbine chamber is preferably symmetrical to the longitudinal center axis, i.e., the mathematical center of gravity of each cross-section between the intake cross-section and the outlet cross-section is approximately located on the longitudinal center axis of the turbine chamber. For achieving more beneficial flow conditions, the center of the outlet window is also approximately located on the longitudinal center axis of the turbine chamber.
In order to moreover minimize dead spaces in the corners of the turbine chamber, the inner longitudinal edges of the turbine chamber are provided with a rounded configuration.
As a result of the relative height position of the outlet cross-section of the turbine chamber, which is positioned higher than the intake window in the partition, the flow through the air turbine is improved. In this connection, the upper edge of the intake window is positioned preferably below the lower edge of the outlet cross-section.
The turbine chamber roof and the turbine chamber bottom are positioned in close proximity to the mantle surface of the air turbine for minimizing fault flows, wherein the distance of the mantle surface to the turbine chamber bottom and to the turbine chamber roof is minimal, respectively, and the two distances are preferably identical.
For an additional lowering of the operating noises it is suggested to provide on the inner wall surface of the turbine chamber wall, in particular, on the inner wall surface of the turbine chamber roof, at least one rib which extends approximately in the flow direction. In this connection, the rib extends from the intake cross-section, in particular, without interruptions, to the outlet cross-section and has preferably the same height along its length. This height substantially bridges the distance between the turbine chamber wall and the air turbine. In this connection, it was found to be advantageous to arrange ribs diametrically opposed to one another relative to the longitudinal center axis; the ribs are positioned in a common plane with the longitudinal center axis. When several ribs are arranged about the inner circumference of the turbine chamber and have preferably the same height, their planes are aligned with the longitudinal center axis of the turbine chamber. This means that all planes of all ribs intersect one another in the longitudinal center axis of the turbine chamber.